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NAME | SYNOPSIS | CONFIGURATION | DESCRIPTION | FILES | SEE ALSO | COLOPHON |
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lp(4) Kernel Interfaces Manual lp(4)
lp - line printer devices
#include <linux/lp.h>
lp[0–2] are character devices for the parallel line printers;
they have major number 6 and minor number 0–2. The minor numbers
correspond to the printer port base addresses 0x03bc, 0x0378, and
0x0278. Usually they have mode 220 and are owned by user root
and group lp. You can use printer ports either with polling or
with interrupts. Interrupts are recommended when high traffic is
expected, for example, for laser printers. For typical dot
matrix printers, polling will usually be enough. The default is
polling.
The following ioctl(2) calls are supported:
int ioctl(int fd, LPTIME, int arg)
Sets the amount of time that the driver sleeps before
rechecking the printer when the printer's buffer appears
to be filled to arg. If you have a fast printer, decrease
this number; if you have a slow printer, then increase it.
This is in hundredths of a second, the default 2 being
0.02 seconds. It influences only the polling driver.
int ioctl(int fd, LPCHAR, int arg)
Sets the maximum number of busy-wait iterations which the
polling driver does while waiting for the printer to get
ready for receiving a character to arg. If printing is
too slow, increase this number; if the system gets too
slow, decrease this number. The default is 1000. It
influences only the polling driver.
int ioctl(int fd, LPABORT, int arg)
If arg is 0, the printer driver will retry on errors,
otherwise it will abort. The default is 0.
int ioctl(int fd, LPABORTOPEN, int arg)
If arg is 0, open(2) will be aborted on error, otherwise
error will be ignored. The default is to ignore it.
int ioctl(int fd, LPCAREFUL, int arg)
If arg is 0, then the out-of-paper, offline, and error
signals are required to be false on all writes, otherwise
they are ignored. The default is to ignore them.
int ioctl(int fd, LPWAIT, int arg)
Sets the number of busy waiting iterations to wait before
strobing the printer to accept a just-written character,
and the number of iterations to wait before turning the
strobe off again, to arg. The specification says this
time should be 0.5 microseconds, but experience has shown
the delay caused by the code is already enough. For that
reason, the default value is 0. This is used for both the
polling and the interrupt driver.
int ioctl(int fd, LPSETIRQ, int arg)
This ioctl(2) requires superuser privileges. It takes an
int containing the new IRQ as argument. As a side effect,
the printer will be reset. When arg is 0, the polling
driver will be used, which is also default.
int ioctl(int fd, LPGETIRQ, int *arg)
Stores the currently used IRQ in arg.
int ioctl(int fd, LPGETSTATUS, int *arg)
Stores the value of the status port in arg. The bits have
the following meaning:
LP_PBUSY inverted busy input, active high
LP_PACK unchanged acknowledge input, active low
LP_POUTPA unchanged out-of-paper input, active high
LP_PSELECD unchanged selected input, active high
LP_PERRORP unchanged error input, active low
Refer to your printer manual for the meaning of the
signals. Note that undocumented bits may also be set,
depending on your printer.
int ioctl(int fd, LPRESET)
Resets the printer. No argument is used.
/dev/lp*
chmod(1), chown(1), mknod(1), lpcntl(8), tunelp(8)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.9.1 2024-05-02 lp(4)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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